Half or more of HIV transmission events may occur within the period of high infectivity (and often high risk behavior) that can last 11 months or more after a person is initially infected. Unfortunately, neither test-and-treat intervention methods nor Acute HIV Infection projects have found effective ways to intervene against transmission during this risky recent infection period. We seek to develop effective intervention techniques against HIV transmission among drug users and their community members during the recent infection period using a combination of drug injection-, sexual- and social-network-based contact tracing methods; community alerts in the networks and venues of recent infectees; and the logic of going up and down infection chains. Our first Aim is to develop and evaluate ways to locate seeds, defined as drug users and other people who have recently been infected. Our second Aim targets members of seeds' networks and people who attend their venues. We will test them for acute and for recent infection, and alert them to the probability that their networks contain highly-infectious members so they should reduce their risk and transmission behaviors for the next several months to minimize their chances of getting infected. This may also reduce transmission by untested people with recent infection. Community, network and venue education about the need and value of supporting those with recent infection should reduce stigma. Our third Aim is to reduce HIV transmission and to develop new ways to evaluate prevention for positives generally as well as our own success in reducing transmission. We will do this using a combination of follow- up interviews and testing, including of viral loads; phylogenetic techniques; and discrete event simulation modeling to assess our effectiveness.